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Risto Väinölä - One of the best experts on this subject based on the ideXlab platform.
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Introgressive hybridization between the Atlantic and Pacific Herrings (Clupea harengus and C. pallasii) in the north of Europe
Marine Biology, 2015Co-Authors: Hanna M. Laakkonen, Petr Strelkov, Dmitry L. Lajus, Risto VäinöläAbstract:We present evidence of mitochondrial and nuclear introgression from the Atlantic Herring Clupea harengus into the Pacific Herring C. pallasii in northern European seas, where the two species have come into secondary contact following the post-glacial trans-Arctic invasion of Pacific Herring to the Atlantic realm. Although the breeding areas of the two species are thought to be separate, 7 % of the resident Pacific Herring in samples from the White Sea were found to possess Atlantic Herring mitochondria. The percentage was even higher (21 %) in the local Balsfjord stock of the Norwegian Sea, whereas it was nil in Pechora Sea samples. Similar or somewhat lower levels of genomic admixture were estimated from four diagnostic or nearly diagnostic nuclear allozyme loci. The absences of inter-locus and cytonuclear disequilibria, together with the patterns of mtDNA haplotype diversity, suggest recurrent backcrossing and hybridization over a long period in the post-glacial time frame. From a reassessment of published allozyme data, a hypothesis is presented that the patterns of intra-species geographical variation previously recorded in North European Herrings may largely reflect varying levels of introgression. The study presents new information on the processes that affect the genetic structure of one of the most abundant fishes of the northern seas. It also adds to the knowledge on the occurrence of inter-species gene flow in marine fishes and on the consequences of trans-Arctic biotic invasions in general.
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phylogeography of amphi boreal fish tracing the history of the pacific Herring clupea pallasii in north east european seas
BMC Evolutionary Biology, 2013Co-Authors: Hanna Laakkonen, Petr Strelkov, Dmitry Lajus, Risto VäinöläAbstract:The relationships between North Atlantic and North Pacific faunas through times have been controlled by the variation of hydrographic circumstances in the intervening Arctic Ocean and Bering Strait. We address the history of trans-Arctic connections in a clade of amphi-boreal pelagic fishes using genealogical information from mitochondrial DNA sequence data. The Pacific and Atlantic Herrings (Clupea pallasii and C. harengus) have basically vicarious distributions in the two oceans since pre-Pleistocene times. However, remote populations of C. pallasii are also present in the border waters of the North-East Atlantic in Europe. These populations show considerable regional and life history differentiation and have been recognized in subspecies classification. The chronology of the inter-oceanic invasions and genetic basis of the phenotypic structuring however remain unclear. The Atlantic and Pacific Herrings both feature high mtDNA diversities (large long-term population sizes) in their native basins, but an ocean-wide homogeneity of C. harengus is contrasted by deep east-west Pacific subdivision within Pacific C. pallasii. The outpost populations of C. pallasii in NE Europe are identified as members of the western Pacific C. pallasii clade, with some retained inter-oceanic haplotype sharing. They have lost diversity in colonization bottlenecks, but have also thereafter accumulated abundant new variation. The data delineate three phylogeographic groups within the European C. pallasii: Herring from the inner White Sea; Herring from the Mezen and Chesha Bays; and a strongly bottlenecked peripheral population in Balsfjord of the Norwegian Sea. The NE European outposts of C. pallasii are judged to be early post-glacial colonists from the NW Pacific. A strong regional substructure has evolved since that time, in contrast to the apparent broad-scale uniformity maintained by Herrings in their native basins. The structure only partly matches the previous biological concepts based on seasonal breeding stocks or geographical subspecies designations. The trans-Arctic Herring phylogeography is notably similar to those of the amphi-boreal mollusk taxa Macoma and Mytilus, suggesting similar histories of inter-oceanic connections. We also considered the time dependency of molecular rates, critical for interpreting timing of relatively recent biogeographical events, by comparing the estimates from coding and non-coding mitochondrial regions of presumably different mutation dynamics.
Jason S. Link - One of the best experts on this subject based on the ideXlab platform.
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role of egg predation by haddock in the decline of an atlantic Herring population
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: David E. Richardson, Jonathan A Hare, Michael J Fogarty, Jason S. LinkAbstract:Theoretical studies suggest that the abrupt and substantial changes in the productivity of some fisheries species may be explained by predation-driven alternate stable states in their population levels. With this hypothesis, an increase in fishing or a natural perturbation can drive a population from an upper to a lower stable-equilibrium population level. After fishing is reduced or the perturbation ended, this low population level can persist due to the regulatory effect of the predator. Although established in theoretical studies, there is limited empirical support for predation-driven alternate stable states in exploited marine fish populations. We present evidence that egg predation by haddock (Melanogrammus aeglefinus) can cause alternate stable population levels in Georges Bank Atlantic Herring (Clupea harengus). Egg predation by haddock explains a substantial decoupling of Herring spawning stock biomass (an index of egg production) from observed larval Herring abundance (an index of egg hatching). Estimated egg survival rates ranged from <2–70% from 1971 to 2005. A population model incorporating egg predation and Herring fishing explains the major population trends of Georges Bank Herring over four decades and predicts that, when the haddock population is high, seemingly conservative levels of fishing can still precipitate a severe decline in the Herring population. These findings illustrate how efforts to rebuild fisheries can be undermined by not incorporating ecological interactions into fisheries models and management plans.
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an ecosystem approach for assessment advice and biological reference points for the gulf of maine georges bank atlantic Herring complex
North American Journal of Fisheries Management, 2008Co-Authors: William J. Overholtz, Larry D. Jacobson, Jason S. LinkAbstract:Abstract The biomass of Atlantic Herring Clupea harengus in the Gulf of Maine–Georges Bank (GOM–GB) region declined sharply in the mid- to late 1970s, when fishery harvests ranged from 300 to 400 kilo–metric tons (kt) per year. During this same period, the consumption of Atlantic Herring by fish and marine mammal predators was very large. Consumption has greatly exceeded landings from 1985 to the present. Previous research showed that four groups of predators (demersal fishes, marine mammals, large pelagic fishes, and seabirds) together annually consumed over 200 kt of Atlantic Herring during the 1970s and over 300 kt during the late 1990s and early 2000s. Our analyses indicate that Atlantic Herring predation mortality rates are related to the abundance of both Atlantic Herring and predators. Predation mortality rates were relatively low during the 1960s, when Atlantic Herring were abundant, but increased in the late 1970s and early 1980s, when Atlantic Herring declined. Predation mortality rates declined...
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The Dynamic Role of Pollock (Pollachius virens) as a Predator in the Northeast US Continental Shelf Ecosystem: a Multi-decadal Perspective
Journal of Northwest Atlantic Fishery Science, 2007Co-Authors: M. C. Tyrrell, Jason S. Link, Hassan Moustahfid, Brian E. SmithAbstract:The Northeast US continental shelf ecosystem has been subject to heavy fishing pressure and other anthropogenic influences that have directly and, through food web interactions, indirectly affected the abundance of fish and invertebrates. The role of pollock (Pollachius virens) as one of the key groundfish predators in this ecosystem has changed accordingly over the last three decades. We utilized a thirty-three year food habits database with over 5 500 pollock stomachs to examine relative removal of commercially valuable fish and invertebrate prey by pollock. Pollock diet composition has substantially shifted through time and appears closely tied to the relative availability of prey. Pollock diet shifted from euphausiids, squid and sandlance early in the time series to decapod shrimp, Herrings and hakes in recent years. Both small and large size classes of pollock have shown an increased proportion of fish in the diet through time. Pollock has, at times, exerted notable predatory removals on squid, and to a lesser extent, on Herring and mackerel. The implications of pollock consumption on prey population dynamics is discussed in light of the recent trend of its increasing biomass.
James R Winton - One of the best experts on this subject based on the ideXlab platform.
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factors controlling the early stages of viral haemorrhagic septicaemia epizootics low exposure levels virus amplification and fish to fish transmission
Journal of Fish Diseases, 2011Co-Authors: Paul K Hershberger, J L Gregg, C A Grady, Lucas M Hart, Sean R Roon, James R WintonAbstract:Viral haemorrhagic septicaemia virus, Genogroup IVa (VHSV), was highly infectious to Pacific Herring, Clupea pallasii (Valenciennes), even at exposure doses occurring below the threshold of sensitivity for a standard viral plaque assay; however, further progression of the disease to a population-level epizootic required viral amplification and effective fish-to-fish transmission. Among groups of Herring injected with VHSV, the prevalence of infection was dose-dependent, ranging from 100%, 75% and 38% after exposure to 19, 0.7 and 0.07 plaque-forming units (PFU)/fish, respectively. Among Pacific Herring exposed to waterborne VHSV (140 PFU mL(-1) ), the prevalence of infection, geometric mean viral tissue titre and cumulative mortality were greater among cohabitated Herring than among cohorts that were held in individual aquaria, where fish-to-fish transmission was prevented. Fish-to-fish transmission among cohabitated Herring probably occurred via exposure to shed virus which peaked at 680 PFU mL(-1) ; shed virus was not detected in the tank water from any isolated individuals. The results provide insights into mechanisms that initiate epizootic cascades in populations of wild Herring and have implications for the design of VHSV surveys in wild fish populations.
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epizootiology of viral hemorrhagic septicemia virus in pacific Herring from the spawn on kelp fishery in prince william sound alaska usa
Diseases of Aquatic Organisms, 1999Co-Authors: Paul K Hershberger, Richard M Kocan, Nancy Elder, T R Meyers, James R WintonAbstract:Both the prevalence and tissue titer of viral hemorrhagic septicemia virus (VHSV) increased in Pacific Herring Clupea pallasi following their introduction into net pens (pounds) used in the closed pound spawn-on-kelp (SOK) fishery in Prince William Sound, Alaska. VHSV was also found in water samples from inside and outside the SOK pounds after Herring had been confined for several days; however, water samples taken near wild free-ranging, spawning Herring either failed to test positive or tested weakly positive for virus. Little or no virus was found in tissue samples from free-ranging, spawning Herring captured from the vicinity of the pounds, nor did the prevalence of VHSV increase following spawning as it did in impounded Herring. The data indicated that increased prevalences of VHSV were correlated with confinement of Herring for the closed pound SOK fishery and that infection was spread within the pounds through waterborne exposure to virus particles originating from impounded fish. In addition, pounds containing predominantly young fish had higher prevalences of VHSV, suggesting that older fish may be partially immune, perhaps as a result of previous infection with the virus. Operation of SOK pounds during spawning seasons in which young Herring predominate may amplify the disease and possibly exacerbate the population fluctuations observed in wild Herring stocks.
Paul K Hershberger - One of the best experts on this subject based on the ideXlab platform.
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factors controlling the early stages of viral haemorrhagic septicaemia epizootics low exposure levels virus amplification and fish to fish transmission
Journal of Fish Diseases, 2011Co-Authors: Paul K Hershberger, J L Gregg, C A Grady, Lucas M Hart, Sean R Roon, James R WintonAbstract:Viral haemorrhagic septicaemia virus, Genogroup IVa (VHSV), was highly infectious to Pacific Herring, Clupea pallasii (Valenciennes), even at exposure doses occurring below the threshold of sensitivity for a standard viral plaque assay; however, further progression of the disease to a population-level epizootic required viral amplification and effective fish-to-fish transmission. Among groups of Herring injected with VHSV, the prevalence of infection was dose-dependent, ranging from 100%, 75% and 38% after exposure to 19, 0.7 and 0.07 plaque-forming units (PFU)/fish, respectively. Among Pacific Herring exposed to waterborne VHSV (140 PFU mL(-1) ), the prevalence of infection, geometric mean viral tissue titre and cumulative mortality were greater among cohabitated Herring than among cohorts that were held in individual aquaria, where fish-to-fish transmission was prevented. Fish-to-fish transmission among cohabitated Herring probably occurred via exposure to shed virus which peaked at 680 PFU mL(-1) ; shed virus was not detected in the tank water from any isolated individuals. The results provide insights into mechanisms that initiate epizootic cascades in populations of wild Herring and have implications for the design of VHSV surveys in wild fish populations.
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doi:10.1155/2011/926812 Research Article Energetic Cost of Ichthyophonus Infection in Juvenile Pacific Herring (Clupea pallasii)
2011Co-Authors: Johanna J. Vollenweider, Jake L. Gregg, Ron A. Heintz, Paul K HershbergerAbstract:Copyright © 2011 Johanna J. Vollenweider et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The energetic costs of fasting and Ichthyophonus infection were measured in juvenile Pacific Herring (Clupea pallasii) inalab setting at three temperatures. Infected Herring incurred significant energetic costs, the magnitude of which depended on fish condition at the time of infection (fat versus lean). Herring that were fed continually and were in relatively good condition at the time of infection (fat) never stored lipid despite ad libitum feeding. In feeding Herring, the energetic cost of infection was a 30% reduction in total energy content relative to controls 52 days post infection. Following food deprivation (lean condition), infection caused an initial delay in the compensatory response of Herring. Thirty-one days after re-feeding, the energetic cost of infection in previously-fasted fish was a 32 % reduction in total energy content relative to controls. Body composition of infected Herring subsequently recovered to some degree, though infected Herring never attained the same energy content as their continuously fed counterparts. Fifty-two days after re-feeding, the energetic cost of infection in previously-fasted fish was a 6 % reduction in total energy content relative to controls. The greatest impacts of infection occurred in colder temperatures, suggesting Ichthyophonusinduce
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epizootiology of viral hemorrhagic septicemia virus in pacific Herring from the spawn on kelp fishery in prince william sound alaska usa
Diseases of Aquatic Organisms, 1999Co-Authors: Paul K Hershberger, Richard M Kocan, Nancy Elder, T R Meyers, James R WintonAbstract:Both the prevalence and tissue titer of viral hemorrhagic septicemia virus (VHSV) increased in Pacific Herring Clupea pallasi following their introduction into net pens (pounds) used in the closed pound spawn-on-kelp (SOK) fishery in Prince William Sound, Alaska. VHSV was also found in water samples from inside and outside the SOK pounds after Herring had been confined for several days; however, water samples taken near wild free-ranging, spawning Herring either failed to test positive or tested weakly positive for virus. Little or no virus was found in tissue samples from free-ranging, spawning Herring captured from the vicinity of the pounds, nor did the prevalence of VHSV increase following spawning as it did in impounded Herring. The data indicated that increased prevalences of VHSV were correlated with confinement of Herring for the closed pound SOK fishery and that infection was spread within the pounds through waterborne exposure to virus particles originating from impounded fish. In addition, pounds containing predominantly young fish had higher prevalences of VHSV, suggesting that older fish may be partially immune, perhaps as a result of previous infection with the virus. Operation of SOK pounds during spawning seasons in which young Herring predominate may amplify the disease and possibly exacerbate the population fluctuations observed in wild Herring stocks.
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Pathogenicity of Ichthyophonus hoferi for laboratory-reared Pacific Herring Clupea pallasi and its early appearance in wild Puget Sound Herring.
Diseases of aquatic organisms, 1999Co-Authors: Richard M Kocan, Paul K Hershberger, Nancy Elder, T. Mehl, M. Bradley, D. Wildermuth, K. StickAbstract:Laboratory-reared pathogen-free Pacific Herring were exposed to pure cultures of Ichthyophonus hoferi, and reproduced the disease seen in naturally infected fish--thus fulfilling Koch's Postulates. Pathogen-free Herring used in this study were reared from artificially spawned eggs incubated in filtered, UV-sterilized seawater, eliminating the variables associated with multiple infections, which are common in wild Herring. Wild free-ranging Herring were captured monthly from June through October by dip net from 'Herring balls' located in the northern Puget Sound. I. hoferi infections were identified in these fish soon after metamorphoses, about 4 mo post-hatch. The prevalence increased from 5 to 6% in 0-yr fish to 24% in 1-yr-old fish to 50 to 70% in fish over 2 yr old, with no associated increase in mortality. The route of natural transmission to wild Herring was not determined, but carnivorous fish became infected and died when they were experimentally fed tissues infected with the organism. In vitro culture of tissues was the most sensitive method for identifying both clinical and subclinical infections.
Georgs Kornilovs - One of the best experts on this subject based on the ideXlab platform.
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discrimination of western baltic spring spawning and central baltic Herring clupea harengus l based on growth vs natural tag information
Ices Journal of Marine Science, 2013Co-Authors: Tomas Grohsler, Rainer Oeberst, Matthias Schaber, Niklas Larson, Georgs KornilovsAbstract:In the Baltic Sea, several stocks of Herring (Clupea harengus L.) are surveyed and managed separately. For assessment purposes, a spatial stock separation based on ICES subdivisions is implemented. However, especially in the western Baltic, the distribution areas of two stocks, the western Baltic spring-spawning Herring and the central Baltic Herring, overlap. Results of regularly conducted surveys for assessment purposes indicated variable degrees of mixing of both stocks in the survey area, based on conspicuous differences in weights/lengths within certain age groups, especially in an area known for overlapping distribution of both stocks. At present, varying fractions of the central Baltic Herring stock have not been taken into account during regular surveys conducted in the western Baltic, leading to possible undetected biases in assessment indices derived from these surveys. Additionally, methods otherwise applied for stock separation of Baltic Herring so far are based on parameters that cannot readily be derived during regular surveys. In this paper, we present a simple and quick method to reliably allocate Herring to either stock based on a separation function derived from survey-based length-at-age data, thus facilitating a more precise estimate of biomass and abundance indices from regular surveys and commercial fisheries.
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linking fisheries trophic interactions and climate threshold dynamics drive Herring clupea harengus growth in the central baltic sea
Marine Ecology Progress Series, 2010Co-Authors: Michele Casini, Valerio Bartolino, Juan Carlos Molinero, Georgs KornilovsAbstract:How multiple stressors influence fish stock dynamics is a crucial question in ecology in general and in fisheries science in particular. Using time-series covering a 30 yr period, we show that the body growth of the central Baltic Sea Herring Clupea harengus, both in terms of condition and weight-at-age (WAA), has shifted from being mainly driven by hydro-climatic forces to an inter- specific density-dependent control. The shift in the mechanisms of regulation of Herring growth is triggered by the abundance of sprat, the main food competitor for Herring. Abundances of sprat above the threshold of ~18 × 10 10 ind. decouple Herring growth from hydro-climatic factors (i.e. salin- ity), and become the main driver of Herring growth variations. At high sprat densities, Herring growth is considerably lower than at low sprat levels, regardless of the salinity conditions, indicative of hys- teresis in the response of Herring growth to salinity changes. The threshold dynamic accurately explains the changes in Herring growth during the past 3 decades and in turn contributes to elucidate the parallel drastic drop in Herring spawning stock biomass. Studying the interplay between differ- ent stressors can provide fundamental information for the management of exploited resources. The management of the central Baltic Herring stock should be adaptive and take into consideration the dual response of Herring growth to hydro-climatic forces and food-web structure for a sound eco- system approach to fisheries.